1. Field of the Invention
The present invention relates to an apparatus for simultaneously punching multiple holes in a ceramic substrate used to produce multi-layer ceramic (MLC) substrates for integrated circuit chips.
2. Description of Related Art
The trend in ceramic electronic packaging of multilayer ceramic substrates is toward "flip chip" technology, also known as controlled collapse chip contact/connection C-4, with extremely high chip/substrate interconnect point counts. As a result, packages need to have high via counts concentrated in the relatively small area where the chip attaches to the substrate.
When punching via holes in green ceramic sheets, there has typically been utilized a punch apparatus in which a magnetically operated solenoid moves a punch rod, the lower end of which is coaxially aligned with a punch. The solenoid causes the pushrod to move up and down in individual strokes to cause the punch to punch a via hole in the ceramic greensheet aligned with a die plate under the substrate. An annular magnet coaxially aligned with the punch maintains the punch in the up position between strokes. It has been known to utilize a plurality of such coaxially aligned solenoid/punch mechanism to punch via holes in MLC substrates. For example, a die set may contain a plurality of punches arranged in a manner that match, as closely as possible, the pattern of via holes required on the product. A technique to minimize punch stroke counts required of such a die setup is described in IBM Technical Disclosure Bulletin, Vol. 29, No. 5 (October, 1986). While this program with the aforementioned die set operated well in previous MLC via pattern requirements, a problem exists in optimizing die set design to match many new products which contain very dense C-4 cages. The current system has not been able to accommodate die mandates with a minimum punch-to-punch spacing of less than 8 mm. With the dense via requirements of current C-4 cages, for example, containing 800 vias with punch spacing less than 8 mm, there will be required 800 strokes to punch the C-4 cage, one punch at a time.
Bearing in mind the problem and deficiencies of the prior art, it is therefore an object of the present invention to provide a punch mechanism which may be used to simultaneously punch via holes in a ceramic substrate with punch-to-punch spacing of less than 8 mm.
It is another object of the present invention to provide a punch mechanism which permits punches to be placed very close together, with several punches within a chip attach area, and still allow each punch to be individually selectable for punching a via hole.
It is another object of the present invention to provide an improved punch mechanism with the above advantages and which permits the punches to be placed in a grid of at least two-by two punches with spacing comparable to that of the via holes for C-4 chip technology.
It is a further object of the present invention to provide a punch mechanism which may be programmable to individually and simultaneously operate one or more of a multiple punch die setup to increase throughput where via holes are very closely spaced.
It is yet another object of the present object to provide a multiple punch mechanism arranged in a grid which permits several punches to be extended at every punch stroke.
It is a further object of the present invention to provide a programmable punch mechanism in which the punches are selectively and simultaneously operable by solenoids.